1) Field of the Invention
The present invention relates to a seal of a vertical pump, and more particularly to a structure having a non-contact and improved labyrinth seal disposed on the impeller.
2) Description of the Prior Art
As indicated in FIGS. 1 and 2, a traditional pump is used at a chemical engineering site for pumping and delivering strong acid, alkali, and corrosive liquid. A cantilever shaft (200) disposed at the front end of a motor (100); a V-type oil seal (300) or a lip seal is disposed near the tail end of the cantilever shaft (200). The main purpose of the seal device is to block the acid and alkali liquid because the V-type oil seal (300) becomes ineffective once it contacts the liquid, especially liquid that crystallizes. That would further corrode an axle center of the motor (100). The front end of the cantilever shaft (200) vertically connects with an axle center of an impeller (400); the backside of the impeller (400) is disposed with a back vane (401). In addition, a front casing (500) is inserted on a main casing; a suction inlet (501) is disposed axially on the front casing (500) opposite the motor (100); a water outlet (502) is disposed on opposite the impeller (400) to engage a discharge pipe (600). The suction inlet (501) and the water outlet (502) are in communication with a volute chamber (700). In an actual implementation, a liquid flows axially from the axial suction inlet (501) toward the impeller (400) which rotates to operate; the volute chamber (700) gathers high pressure liquid and conducts it through the water outlet (502). However, the conventional vertical pump has two shortcomings:
1. It uses the back vane (401) to eliminate the back pressure of the impeller (400). However, the back vane (401) stirs the air and the delivery liquid to create a lot of air bubbles; the air bubbles tremendously increase the defect rate during the manufacturing process of a printed circuit board.
2. When the pump stops and the back vane (401) is not working, the liquid flows toward the V-type seal (300) above the liquid surface in a similar water hammer effect. If the liquid left on the seal device crystallizes, it damages the V-type seal (300) device or the lip seal. Although some manufacturers suggested the use of a check valve to solve this problem, most of the machines do not have enough space for installation, and the crystallization might make the check valve inefficient.